订阅本博客

搜索博客文章

博客文章列表

Filtering cartridges are very common products used in many industrial processes to clarify/decontaminate a broad variety of liquids (beverage, pharmaceutics, chemicals, paints, varnishes, blood, drinking water,…) and on as many types of machines (aircrafts, engines, boats, fluid power systems, road and off-road vehicles, machine tools,…).

If efficient, all filtering cartridges, whatever their type, clog, what means their differential pressure increases and/or flowrate decays. Then they cannot fulfil their function correctly and need being replaced. This creates a huge market of renewable products with plenty of suppliers offering very diverse cartridges.

Criteria to choose a cartridge and its supplier rather than another one strongly depend on its application. But in all cases, the key criterion is filtration efficiency. another one possibly being retention capacity.

Filtration efficiency guarantees the quality of the filtered liquid. It is specified/expressed by a percentage of efficiency in percent or a filtration ratio (e.g. ß) at a given particle size or by a rating, i.e. a particle size supposed to correspond to a given, often not claimed, efficiency.

Since the efficiency measurement method, equipment and products directly impact the values of efficiency, many professional sectors, including filter cartridge manufacturers and their end users agree on standard methods, often a compromise between technical and cost requirements, such as ASTM, NFPA, SAE or ISO standards.

All standard procedures allow variations of different details, e.g. accuracy of measuring instruments, variations in test conditions, type of equipment, validation criteria, etc. This means that performances claimed according to any standard by any manufacturer may not be comparable to those claimed by a competitor for the same application.

Thus only independent third party testing centre results can really be trusted when evaluating competing products.

When used in solid-liquid and liquid-liquid separation applications filters serve a critical function to ensure process quality and repeatability. Whether it could remove the particulates that can damage equipment or remove water from fuel to extend system service life is very important. Improper filter design and filter media selection can result in catastrophic failure.

The concept that filters have a specific "DNA" may seem odd but just as Deoxyribonucleic Acid ("DNA') defines the nature of the human body, there is a "DNA" associated with a filter that defines how it will perform. Filters are used to separate many different particles and liquids. The effectiveness and efficiency of filters can be determined by laboratory testing before expensive plant modifications are made for real world use. For instance, most filters and filter media have an "unloading point" that is a measureable differential pressure at which filters release trapped contaminants downstream. The correct testing can find these "unloading points". These released downstream particulates can erode or ruin an engine, cause scrap in food and beverage processing, or may even seize mechanical system components. Even before the burst point where the particulates downstream increase, due to change in pressure or other external conditions, can still destroy the system. Each filter has its own attributes and to determine them you need to consider multiple tests to define the "DNA" of a filter.

The testing to determine the "DNA" of a filter is much more inclusive than simple initial efficiency, mean pore flow or bubble point testing techniques. While these provide a good starting point, “DNA” testing is more holistic than the above-mentioned tests that provide only one small detail about the filter. The idea of knowing more about a filter is essential in determining where the filter would perform the best and where it will perform the worst. “DNA” tests using international standards provide results that are repeatable and allow “apple to apple” comparison with other filters and their applications.

The “DNA” of a filter is formed from the results of various tests depending on the process application.

Filter is a consumable product which needs replacing termly, the market is huge; the competition is very fierce. Almost each filter manufacturer has many competitors in different application fields. Undoubtedly, each filter manufacturer hopes to gain more business by proving to the customer that their own products have better cost performance than their competitor(s).

Analyse the performance of competitor’s product, compare with their own product and the customers’ requirement is the most common strategy. Many filter manufacturers invest their own test lab that has the capability of facing to the OEM customers; they buy testing equipments for research & development works and the analysis of competitors. During the certificating process by the OEM customers (filter users), test ability is an indispensable part.

But, there have so many testing items for a filter. No one could equip all the test equipments. And there also exist the risk to the filter manufacturer when they developing new OEM customer, they need to prove to the customer their lab is capable and trustable. A smart filter manufacturer will evaluate the quantity of each test item instead of invest the test equipments blindly; Even they have the test ability for a test item, some manufacturers prefer to choose presenting test report by the third party lab, it is helpful to impress the customer and shows the ability of themselves.

IFTS founded in 1981, it is a fully independent and professional liquid filter testing organization; Acting as the Europe filter testing centre and the world reference lab, IFTS is in service to hundreds of the customers around the world. Filter manufacturers use IFTS’s third party testing report to prove the performance of their product(s) to the customer, the filter users use IFTS’s services for monitoring the performance of the suppliers. There have some successful stories that the manufacturers gained the good business without investing the test equipments.

Recently, we have got some inquires for fuel filter testing according to ISO/TR 13353(1994) from the customers in China, they asked us to run test for them according to this standard.

ISO/TR 13353(1994) is an old test standard which has already been withdrew on August 29th of 2002. We explained that we have some more ACFTD available by IFTS and we can correlate from µm(c) to µm. That is the reason why we can work according to this old standard.

These Chinese customer told us their customers (the filter end users) ask them to use this standard to test the fuel filter.

This article introduces the upgrading of this testing standard for diesel fuel filters. Try to help filter users and filter manufacturers to understand the background of this testing standard.

ISO/TR 13353(1994) was founded by IFTS and accepted by BOSCH in 1994. It is in order to qualify the filtration efficiency and the retention capacity of fuel filters. This procedure is divided in two parts: a first one is dedicated with the determination of the initial filtration efficiency (singlepass circulation at 5 mg/L of ACFTD – expression of the filtration ratings in µm); The second one is dedicated with the determination of the retention capacity (multipass recirculation at 50 mg/L of ACFTD up to an increase of DP of 70 kPa).

Since 1999, the ACFTD no more available ; it has been replaced by ISO MTD and the calibration for the APC (automatic particle counter) has been upgraded: the ISO 4402(1991) has been revised by the ISO 11171(1999). About dust history, please read here.

ISO/TS 13353(2002) has been reviewed and is only dealing with the determination of the initial filtration efficiency (according to a BUGL of 5 mg/L of ISO MTD in a single pass way – expression of the filtration ratings in µm(c) ).

ISO 19438 (2003) has been standardised for determining both the filtration efficiency and the retention capacity with working in a multipass recirculation with a BUGL of 50 mg/L of ISO MTD and on line dilution concerning particle counting – expression of the filtration ratings in µm(c) ).

That is to say, nowadays, ISO/TR 13353 (1994) is no more available. Has been replaced by ISO 19438(2003).

Last round robin tests in 2004 have proven that the determination of the initial filtration efficiency is similar whatever using ISO/TS 13353 (2002) or ISO 19438 (2003). Normally, including BOSCH, the fuel filter users should make the specification with using ISO 19438 procedure.

All above standards’ upgrading, you could find records on the official ISO website. For example, you could find the revision information for ISO/TS 13353(2002) in below image, it revised ISO/TR 13353(1994) and has been revised by ISO 19438:

For more detailed historical background, we suggest you to refer to ISO/TR 16386(1999).

Liquid filter media all have the same role of letting the liquid flow through whilst retaining a part if not all particles in suspension. Liquid filtration occurs in a very broad variety of processes and equipments, from engines fuel or lubricating oil to drinking water through chemicals, blood or varnishes.

Depending on the type of filter used, filtering media are of made of layers of grains (sand or diatomites) or of fibers, which can be wound or processed or papers.

The variety of techniques, processes and liquids they are applied to create a broad spectrum of technical requirements and properties. Tests are developed to evaluate these properties in accelerated conditions, cheaper and much faster than actual operation ones.

The lecture will present an overview of the characteristics of filter media (from granular ones to sterilizing membranes) classified in four families: intrinsical relating to the internal structure of the porous media, hydraulic which cover the impact of the media on the fluid flow, performances, i.e. how the media retains particles or undesirable substances and the impact of their retention on both the permeability and the efficiency and compatibilities, including all “negative” interactions between the media material and the filtered fluid.

Main test procedures (especially standard ones) will be summarised. A brief presentation will be made of their principles, of the equipments and products used, of the criteria of validation of test benches.

The way raw data have to be processed to obtain standard test report will be explained and typical interpretation of data oriented toward the optimisation of the choice of filtering media will be given.